The present invention relates in general to continuous dough proofers, and more particularly, to improvements in unloading pusher bar assemblies used in continuous dough proofers.
U.S. Pat. Nos. 3,620,352 and 3,349,928 disclose dough proofers of the type in which successive rows of pans of dough are charged onto vertically spaced shelves of racks, and which racks are movable through a proofing chamber to a point of discharge of the pans of proofed dough.
The proofers disclosed in the just-mentioned patents use a discharge pusher assembly for moving a row of pans containing proofed dough from the proofer, and the pusher assemblies include a kinematic linkage which converts rotary motion of a motor into linear reciprocating motion of a pusher bar. The pusher bar contacts a row of pans containing proofed dough and moves that row of pans from the proofer onto a discharge conveyor.
The kinematic linkages disclosed in these patents include a crank arm coupled to a pusher bar operating arm by a cam follower on the crank arm which is slidably received in a cam slot defined in the operating arm. The operating arm is pivotally connected to a proofer frame member, and, as the crank arm is rotated by the motor, the operating arm pivots and operates the pusher bar.
The slots in the operating arms of these patents are straight and thus, the speed of the pusher bar varies sinusoidally with distance throughout the stroke thereof. Thus, the pusher bar starts out slowly from the rest, or home position, and speeds up until the forward stroke half-way position of the unloading phase is reached. At this half-way position, the pusher bar is moving at the maximum stroke speed. After passing the half-way position, the pusher bar stroke speed decreases to zero at the stroke reversal position. The sine curve shape of the stroke speed produces desirable unloading pusher cycle time advantages.
The pan straps P, shown in U.S. Pat. No. 3,620,352 or in U.S. Pat. No. 2,590,823, can have a variety of lengths depending upon the number of individual pans contained in a pan strap. Furthermore, the overall length of a single pan strap may also vary due to variations in the spacing between pans of different runs of pan sets or in the widths of the pans in different runs of pan sets.
The pusher arm in U.S. Pat. No. 3,620,352 is arranged to have a pushing stroke of a length sufficient to move a row of pans onto an unloading conveyor. The pusher bar travels a short distance, then contacts the pan during the unloading stroke. As above-discussed, the pusher bar accelerates as it travels forwardly on the discharge stroke. Thus, the impact between the pusher bar and the pan increases as the contact position is moved farther toward the forward stroke half-way position from the pusher bar starting position. As pan strap overall length varies, the contact point varies.
If the pusher bar stroke is set up to accommodate the longest pan strap, any shorter pan strap length will cause the pan-bar impact to increase. Proofed dough is sensitive to shock, and the bar-pan impact must be sufficiently low so that the danger of the proofed raised dough falling is not presented. The variation in pan strap length can be as much as 10 inches, and thus the short pans may receive an impact which is quite large in relation to the impact received by the long pans.
It is desirable to maintain the pan-bar impact within safe ranges for all pan strap lengths encountered, while retaining the cycle time advantages of a sinusoidally shaped pusher stroke speed curve without sacrificing cycle times associated with long pan straps.